US20070230226A1 - Multilevel intelligent universal auto-transformer - Google Patents
Multilevel intelligent universal auto-transformer Download PDFInfo
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- US20070230226A1 US20070230226A1 US11/705,077 US70507707A US2007230226A1 US 20070230226 A1 US20070230226 A1 US 20070230226A1 US 70507707 A US70507707 A US 70507707A US 2007230226 A1 US2007230226 A1 US 2007230226A1
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
- H02M5/40—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc
- H02M5/42—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters
- H02M5/44—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac
- H02M5/453—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal
- H02M5/458—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M5/4585—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only having a rectifier with controlled elements
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/483—Converters with outputs that each can have more than two voltages levels
- H02M7/487—Neutral point clamped inverters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/66—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal
- H02M7/68—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters
- H02M7/72—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/79—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/797—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
Definitions
- the present invention relates generally to power conversion technology and in particular to a universal autotransformer for enhancing the functionality of power conversion.
- Transformers have numerous applications including voltage or current conversion, impedance matching and electrical isolation. As a consequence, transformers are widely used throughout the world, forming the backbone of electric power conversion systems, and make up a large portion of power delivery systems.
- the positive attributes of conventional transformers have been well documented for years and include low cost, high reliability, and high efficiency. Were it not for these highly reliable devices, activities such as recharging batteries in a portable device or consumers receiving power from a distant electric generator would be prohibitively expensive, resulting in electricity being a much less practical form of energy.
- FIG. 1 illustrates a conventional autotransformer 100 that may be used to convert an input V 1 110 , having a first ac voltage and current level and a first frequency, to an output V 2 112 , having a second ac voltage and current level and a second frequency equal to the first frequency.
- Conventional autotransformers such as the conventional autotransformer 100 , typically utilize a copper and iron-based core to perform such a power transformation.
- the second ac voltage and current level may be adjusted by selecting a number of windings or taps in the core that are coupled to the output V 2 112 .
- the first voltage of the input V 1 110 is typically higher than the second voltage of the output V 2 112 .
- Power typically flows only from the primary side to the secondary side.
- the voltage of the output V 2 112 drops under load; there is a sensitivity to harmonics generated in a load; environmental impacts occur if mineral oil in the core leaks; there is little or no flexibility in adjusting the power conversion (including voltages/currents, and/or the first or second frequencies); and there is no energy-storage capacity.
- One consequence of not having energy storage capacity is that the output V 2 112 can be easily interrupted because of a disturbance at the input V 1 110 .
- a multilevel intelligent universal transformer includes power electronics on a primary side and on a secondary side to enhance the functionality of power conversion.
- the multilevel intelligent universal transformer may be an auto-transformer.
- a power conversion device includes a first switched converter circuit coupled to a device input and a second switched converter circuit coupled to the first switched converter circuit and a device output.
- the first switched converter circuit and the second switched converter circuit may be configurable for multi-level step-up and/or step-down conversion.
- the first switched converter circuit and the second switched converter circuit may be configured to utilize duty-cycle modulation to implement the multi-level step-up and/or step-down conversion.
- An energy storage device e.g., ultra-capacitor
- the first switched converter circuit may be coupled between the first switched converter circuit and the second switched converter circuit to mitigate voltage disturbances.
- a first filter may be coupled to an input of the first switched converter circuit and/or a second filter may be coupled to an output of the second switched converter circuit.
- the first filter and the second filter may be configured to provide substantially sinusoidal signals.
- the first switched converter circuit may include a first plurality of configurable semiconductor switches and second switched converter circuit may include a second plurality of configurable semiconductor switches.
- the first switched converter circuit is configured to adjust a first number of conversion levels of signals at the device input, and/or the second switched converter circuit is configured to adjust a second number of conversion levels of signals at the device output.
- the first switched converter circuit is a half-bridge or a full-bridge converter.
- the second switched converter circuit is a half-bridge or a full-bridge converter.
- the device is configurable for bidirectional power flow. In some embodiments, a frequency of signals at the device output is configurable.
- the first switched converter circuit is configured to receive signals at the device input having 3-phases separated by approximately 120°.
- the second switched converter circuit is configured to output signals at the device output having 3-phases separated by approximately 120°.
- a significant advantage of the present invention is the combining of the functionalities of one or more custom power devices into a single, tightly integrated, electrical device, rather than the costly conventional solution of utilizing separate custom power devices.
- FIG. 1 is a circuit diagram illustrating a conventional auto-transformer
- FIG. 2 is a circuit diagram illustrating an embodiment of a universal transformer
- FIG. 3 is a circuit diagram illustrating an embodiment of a universal transformer
- FIG. 4 is a circuit diagram illustrating an embodiment of a universal transformer
- FIG. 5 is a circuit diagram illustrating an embodiment of a universal transformer
- FIG. 6 is a circuit diagram illustrating an embodiment of a universal transformer
- FIG. 7 is a circuit diagram illustrating an embodiment of a universal transformer
- FIG. 8 is a circuit diagram illustrating an embodiment of a control system
- FIG. 9 is a flow diagram illustrating an embodiment of a process of operation of a universal transformer.
- FIG. 10 is a block diagram illustrating an embodiment of a system.
- the universal auto-transformer utilizes modern power electronics to replace the core in a conventional auto-transformer and thereby enhances the power conversion functionality.
- the universal auto-transformer includes a plurality of power semiconductor switches in at least first and second switched converter circuits corresponding to the primary side and the secondary side, respectively, of a conventional auto-transformer.
- the universal auto-transformer may include an energy storage device, such as one or more capacitors, between the first and the second switched converter circuits.
- the energy storage device may serve as the energy buffer in between the source and load to avoid direct impact from either the load to the source or the source to the load.
- the energy storage device may allow the universal auto-transformer to at least partially compensate for outages, where input signals to the universal auto-transformer are temporarily reduced (such as voltage sag) or disrupted.
- the power electronic switches in the first and the second switched converter circuits may allow the universal auto-transformer to be configured in a variety of ways.
- the universal auto-transformer may be configured for one of a range of step-up or step-down voltage and/or current conversions.
- a voltage and/or current of the output signals may be regulated. Harmonics generated by nonlinearities in a load, as seen from the input, may be reduced or eliminated.
- a frequency of the output signals may be adjusted and/or selected (e.g., DC, 50 Hz, 60 Hz, 400 Hz, etc.).
- the input and/or the output signals may be approximately uni-phase or poly-phase, such as tri-phase signals where signals are separated by approximately 120°.
- the universal auto-transformer may be configured for bidirectional power flow. For example, power may flow from the primary side to the secondary side or from the secondary side to the primary side.
- FIG. 2 is a circuit diagram illustrating an embodiment of a universal transformer 200 .
- the universal transformer 200 illustrates a multilevel converter single-phase to single-phase step-down auto-transformer.
- the universal transformer 200 includes a 3-level full-bridge converter 214 , a 3-level half-bridge converter 216 , and an energy storage device 218 .
- the universal transformer 200 has a supply voltage V d , a common voltage V Cd , and a ground GND.
- the 3-level full-bridge converter 214 on the primary side includes two groups of four switches S A 222 and S B 224 , as well as anti-parallel diode protection.
- the 3-level half-bridge converter 216 on the secondary side includes four switches S C 226 and anti-parallel diode protection.
- the energy storage device 218 includes a plurality of capacitors, connected in series, that are in parallel with an output from the 3-level full-bridge converter 214 and an input to the 3-level half-bridge converter 216 .
- the energy storage device 218 may include a battery.
- the energy storage device 218 may be any DC voltage source capable of maintaining voltage for a sufficient period of time to compensate for a disturbance or interruption, such as an outage, and may include capacitor banks, ultra-capacitors, flywheels, batteries, or any other suitable storage media (or any combination thereof). If the universal transformer 200 is used in an application or system that requires outage compensation or short-term interruption protection, the energy storage device 218 may allow the universal transformer 200 to ride-through these disturbances.
- the energy storage device 218 may compensate for the deficit and maintain constant voltage amplitude for an output V 2 212 .
- the total period of compensation as a function of the amount of energy storage may be adapted as desired.
- an additional device, such as a battery, in the energy storage device 218 may be switched into the universal transformer 200 upon detection of a voltage sag and/or to provide outage compensation.
- the universal transformer 200 converts the input V 1 210 to the output V 2 212 .
- Duty cycle modulation of signals (for example, using pulse width modulation) controlling the switches S A 222 , S B 224 , and/or S C 226 allows the step-down voltage (between the input V 1 210 and the output V 2 212 ) to be adjusted and/or configured.
- a common duty cycle is used for control signals to the switches S A 222 , S B 224 , and S C 226 , and a voltage amplitude of the input V 1 210 is approximately twice the voltage amplitude of the output V 2 212 .
- power is flowing from the primary side to the secondary or load side.
- the 3-level full-bridge converter 214 functions as a converter
- the 3-level half-bridge converter 216 functions as an inverter. In other embodiments, power may flow from the secondary side to the primary side.
- the 3-level full-bridge converter 214 functions as a inverter
- the 3-level half-bridge converter 216 functions as a converter
- the input V 1 210 is approximately sinusoidal having the first frequency
- the output V 2 212 is approximately sinusoidal having the second frequency.
- An approximately sinusoidal signal has substantially reduced ripple.
- the first frequency may be different that the second frequency (e.g., DC, 50 Hz, 60 Hz, or 400 Hz) depending on the duty cycle modulation of the switches S A 222 , S B 224 , and/or S C 226 .
- the second frequency e.g., DC, 50 Hz, 60 Hz, or 400 Hz
- other combinations of passive and/or active devices can be coupled to the primary side and/or the secondary side of the universal transformer 200 to provide filtering using well-known filter design techniques.
- the switches S A 222 , S B 224 , and/or S C 226 may be semiconductor switches that may be rapidly switched (approximately at 30,000 to 40,000 Hz).
- the switches S A 222 , S B 224 , and/or S C 226 may include Gate-Turn-Off (GTO) Thyristors, Integrated Gate Bipolar Transistors (IGBTs), MOS Turn-off Thyristors (MTOs), Integrated-Gate Commutated Thyristors (IGCTs), Silicon Controlled Rectifiers (SCRs), or any other semiconductor devices that have a turn-off capability.
- GTO Gate-Turn-Off
- IGBTs Integrated Gate Bipolar Transistors
- MTOs MOS Turn-off Thyristors
- IGCTs Integrated-Gate Commutated Thyristors
- SCRs Silicon Controlled Rectifiers
- the universal transformer 200 will also isolate the voltage of the input V 1 210 and the current from the output V 2 212 .
- transients such as those generated by a power factor correction capacitor switching event, will not propagate to the secondary or load side of the universal transformer 200 .
- harmonics such as those generated in a non-linear load or by reactive power in the load, will not propagate to the primary side. This may be accomplished by actively switching the switches S A 222 and S B 224 in the full-bridge converter 214 such that an input current becomes sinusoidal and in phase with the voltage of the input V 1 210 .
- the universal transformer 200 may include fewer components or additional components. For example, a number of switches and/or their switching frequency may be different from that illustrated in the universal transformer 200 . Functions of two or more components may be combined. An order or relative position of two or more components may be interchanged.
- FIG. 3 is a circuit diagram illustrating an embodiment of a universal transformer 300 .
- the universal transformer 300 converts the input V 1 310 to the output V 2 312 using a 5-level full-bridge converter 314 , a 5-level half-bridge converter 316 , and an energy storage device 318 .
- the universal transformer 300 has a supply voltage V d , a common voltage V Cd , and a ground GND.
- the 5-level full-bridge converter 314 on the primary side includes two groups of eight switches S A 322 and S B 324 , as well as anti-parallel diode protection.
- the 5-level half-bridge converter 316 on the secondary side includes eight switches S C 328 and anti-parallel diode protection.
- the energy storage device 318 includes a plurality of capacitors 326 , connected in series, that are in parallel with an output from the 5-level full-bridge converter 314 and an input to the 5-level half-bridge converter 316 .
- the energy storage device 318 may include an additional device, such as a battery, as described above for the universal auto-transformer 200 ( FIG. 2 ).
- the universal auto-transformer 300 may also include inductors L 1 320 and L 2 330 or other active or passive components to provide filtering of high frequencies signals and/or smoothing of noise.
- switches S A 322 , S B 324 , and S C 328 and the universal auto-transformer 300 (and the switches in the embodiments described below) as a whole is similar to that of the switches S A 222 , S B 224 , and S C 226 ( FIG. 2 ) and the universal auto-transformer 200 ( FIG. 2 ), increasing the number of levels (and switches) has advantages for higher voltage applications.
- Each of the switches S A 322 , S B 324 , and S C 328 only needs to block a quarter of the DC bus voltage.
- the universal transformer 300 may be used with higher high-voltages for the input V 1 310 and/or the output V 2 312 without using higher voltage devices for the switches S A 322 , S B 324 , and/or S C 328 .
- the universal transformer 300 may include fewer components or additional components. For example, a number of switches and/or their switching frequency may be different from that illustrated in the universal transformer 300 . Functions of two or more components may be combined. An order or relative position of two or more components may be interchanged.
- FIG. 4 shows is a circuit diagram of an embodiment of a universal transformer 400 .
- the universal transformer 400 converts the input V 1 410 to the output V 2 412 using an 11-level full-bridge converter 414 , an 11-level half-bridge converter 416 , and an energy storage device 418 .
- the universal transformer 400 has a supply voltage V d , a common voltage V Cd , and a ground GND.
- the 11-level full-bridge converter 414 on the primary side includes two groups of 20 switches S A and S B , as well as anti-parallel diode protection.
- the 11-level half-bridge converter 416 on the secondary side includes 20 switches S C and anti-parallel diode protection.
- the energy storage device 418 includes a plurality of capacitors C, connected in series, that are in parallel with an output from the 11-level full-bridge converter 414 and an input to the 11-level half-bridge converter 416 .
- the energy storage device 418 may include an additional device, such as a battery, as described above for the universal auto-transformer 200 ( FIG. 2 ).
- the universal auto-transformer 400 may also include inductors L 1 420 and L 2 422 or other active or passive components to provide filtering of high frequencies signals and/or smoothing of noise.
- the input V 1 410 is 345 kV and the output V 2 412 is 220 kV.
- the universal transformer 400 may include fewer components or additional components. For example, a number of switches and/or their switching frequency may be different from that illustrated in the universal transformer 400 . Functions of two or more components may be combined. An order or relative position of two or more components may be interchanged.
- FIG. 5 shows an embodiment of a universal transformer 500 .
- the universal transformer 500 converts the input V 1 510 to the output V 2 512 using a 3-level half-bridge converter 514 , a 3-level half-bridge converter 516 , and an energy storage device 518 .
- the universal transformer 500 has a supply voltage V d , a common voltage V Cd , and a ground GND.
- the 3-level half-bridge converter 514 on the primary side includes four switches S A 522 and anti-parallel diode protection.
- the reduced number of switches in this embodiment 500 reduces the overall cost.
- the 3-level half-bridge converter 516 on the secondary side includes four switches S B 524 and anti-parallel diode protection.
- the energy storage device 518 includes a plurality of capacitors, connected in series, that are in parallel with an output from the 3-level half-bridge converter 514 and an input to the 3-level half-bridge converter 516 .
- the energy storage device 518 may include an additional device, such as a battery, as described above for the universal auto-transformer 200 ( FIG. 2 ).
- the universal auto-transformer 500 may also include inductors L 1 520 and L 2 526 or other active or passive components to provide filtering of high frequencies signals and/or smoothing of noise.
- the universal transformer 500 may include fewer components or additional components. For example, a number of switches and/or their switching frequency may be different from that illustrated in the universal transformer 500 . Functions of two or more components may be combined. An order or relative position of two or more components may be interchanged.
- the number of configurable switches on the primary and/or the secondary side of the universal auto-transformer may be selected and/or configured.
- a first number of switches in the converter circuit on the primary side is based on a voltage of signals at the device input and a voltage limit of the switches in the converter circuit on the primary side.
- a second number of switches in the converter circuit on the secondary side is based on a voltage of signals at the device output and a voltage limit of the switches in the converter circuit on the secondary side.
- the first number of switches may be increased if the voltage of signals at the device input is increased and/or the voltage limit of the switches in the converter circuit on the primary side is decreased.
- the first number of switches in the converter on the primary side and/or the second number of switches in the converter on the secondary side may vary based on the design and/or application considerations.
- the first number of switches equals 2(N 1 ⁇ 1), 3(N 1 ⁇ 1), 4(N 1 ⁇ 1), or 6(N 1 ⁇ 1), where N 1 is a number of conversion levels of the signals at the device input.
- the second number of switches equals 2(N O ⁇ 1), 3(N O ⁇ 1), 4(N O ⁇ 1), and 6(N O ⁇ 1), where N O is a number of conversion levels of the signals at the device output.
- N O is a number of conversion levels of the signals at the device output.
- the number of switches in a half-bridge converter circuit may be 4, and the number of switches in a full-bridge converter circuit may be 8.
- full-bridge converters may be used on both the primary and the secondary side of the universal auto-transformer. While the second number of switches is doubled relative to embodiments such as the universal auto-transformer 200 ( FIG. 2 ), the maximum voltage of the output is also doubled.
- FIG. 6 shows an embodiment of a universal transformer 600 .
- the universal transformer 600 converts the input V 1 610 to the output V 2 612 using a 3-level full-bridge converter 614 , a 3-level full-bridge converter 616 , and an energy storage device 618 .
- the universal transformer 600 has a supply voltage V d , a common voltage V Cd , and a ground GND.
- the 3-level full-bridge converter 614 on the primary side includes two groups of four switches S A 622 and S B 624 , as well as anti-parallel diode protection.
- the 3-level full-bridge converter 616 on the secondary side includes two groups of four switches S C 628 and SD 630 , as well as anti-parallel diode protection.
- the energy storage device 618 includes a plurality of capacitors C 626 , connected in series, that are in parallel with an output from the 3-level full-bridge converter 614 and an input to the 3-level full-bridge converter 616 .
- the energy storage device 618 may include an additional device, such as a battery, as described above for the universal auto-transformer 200 ( FIG. 2 ).
- the universal auto-transformer 600 may also include inductors L 1 620 and L 2 632 or other active or passive components to provide filtering of high frequencies signals and/or smoothing of noise.
- the universal transformer 600 may include fewer components or additional components. For example, a number of switches and/or their switching frequency may be different from that illustrated in the universal transformer 600 . Functions of two or more components may be combined. An order or relative position of two or more components may be interchanged.
- the universal auto-transformer may also be configured and/or used to convert single-phase input signals into poly-phased output signals. This is illustrated in FIG. 7 , which shows a circuit diagram illustrating an embodiment of a universal transformer 700 .
- the universal transformer 700 converts the input V 1 710 to a three-phase the output V 2 712 (having approximately 120° between the signals) using a 3-level half-bridge converter 714 , a 3-level half-bridge converter 716 , and an energy storage device 718 .
- the universal transformer 700 has a supply voltage V d , a common voltage V Cd , and a ground GND.
- the 3-level half-bridge converter 714 on the primary side includes four switches S A 722 and anti-parallel diode protection.
- the 3-level half-bridge converter 716 on the secondary side includes three groups of four switches S B 724 , S C 726 , and S D 728 , as well as anti-parallel diode protection.
- the energy storage device 718 includes a plurality of capacitors, connected in series, that are in parallel with an output from the 3-level half-bridge converter 714 and an input to the 3-level half-bridge converter 716 .
- the energy storage device 718 may include an additional device, such as a battery, as described above for the universal auto-transformer 200 ( FIG. 2 ).
- the universal auto-transformer 700 may also include inductors L 1 720 and L 2 730 or other active or passive components to provide filtering of high frequencies signals and/or smoothing of noise.
- the universal transformer 700 may include fewer components or additional components. For example, a number of switches and/or their switching frequency may be different from that illustrated in the universal transformer 700 , such as would be needed if one or more full-bridge converters are used instead of half-bridge converters. Alternatively, poly-phase input signals may be converted into single-phase output signals. Functions of two or more components may be combined. An order or relative position of two or more components may be interchanged.
- the universal auto-transformer 200 is used as an illustrative example of the operation of other embodiments of the universal auto-transformer.
- the basic operation is to switch first pair of switches S A1 222 - 1 and S A2 222 - 2 and second pair of switches S B3 224 - 3 and S B4 224 - 4 , and to switch third pair of switches S A3 222 - 3 and S A4 222 - 4 and fourth pair of switches S B1 224 - 1 and S B2 224 - 2 , in an alternating fashion such that an output of the 3-level half-bridge converter 216 is an alternating chopped DC voltage.
- the switches S C 226 are similarly paired and switched.
- the filter associated with L 2 228 smoothes the resulting chopped DC voltage into a clean, sinusoidal waveform.
- the switches S A 222 , S B 224 , and/or S C 226 may be controlled by an external control means using either analog or digital control signals in a manner commonly known to one of ordinary skill in the art.
- the states of switches S A 222 , S B 224 , and/or S C 226 may be controlled using pulse-width modulation (PWM) techniques.
- PWM pulse-width modulation
- the width of pulses in a pulse train are modified in direct proportion to a small control voltage.
- FIG. 8 is a circuit diagram showing an embodiment of a feedback control system 800 .
- the feedback control system 800 includes a processor 806 (e.g., microcomputer, digital signal processor), a scaling factor circuit 808 , a set of gate drivers 810 , and a command interface 812 .
- the processor further includes a pulse width modulator 814 , a controller 816 , and memory 818 (e.g., DRAM, CD-ROM).
- the scaling factor circuit 808 and the gate drivers 810 isolate control signals from the power.
- the processor 806 compares a command voltage, V ref , and a scaled feedback output signal, V sense , to determine an error signal, V error .
- the feedback signal, V sense is taken from the output of the converter 802 .
- the error signal, V error is received by the controller 816 , which generally applies a proportional (P), proportional-integral (PI), or proportional-integral-differentiator (PID) gain to the error signal.
- the output of the controller is a smooth duty cycle signal, d(t). Note that in a typical application either a load (e.g., adjustable speed drive) or another converter 804 is coupled to the output of the converter 802 .
- the duty cycle of each switch in the converter 802 is computed by the processor 806 based on one or more computer programs or gate pattern logic stored in the memory 818 .
- the resulting duty cycle signal, d(t) is then sent to the pulse width modulator 814 (PWM), which generally includes a set of voltage comparators.
- PWM pulse width modulator 814
- one comparator is used for each pair of switches.
- the switch pair S A1 222 - 1 and S A2 222 - 2 ( FIG. 2 ) in the actively switched full-bridge converter 214 ( FIG. 2 ) may be controlled by a first comparator, and the switch pair S A3 222 - 3 and S A4 222 - 4 ( FIG. 2 ) may be controlled by a second comparator.
- the PWM signals are then fed into the gate drivers 810 to turn the switches in the converter 802 on or off.
- the number of switches in the converter 802 depends on how many voltage levels and phases are to be controlled.
- control voltages d(t) can be varied to achieve different frequencies and voltage levels in any desired manner.
- the processor 806 can implement various acceleration and deceleration ramps, current limits, and voltage-versus-frequency curves by changing variables (e.g., via the command interface 812 ) in control programs or gate pattern logic in processor 806 .
- the PWM circuit 814 will turn on the upper switches (e.g., switches S A1 222 - 1 and S A2 222 - 2 ) of the full-bridge converter 214 ( FIG. 2 ) and turn off the lower switches (e.g., switches S A3 222 - 3 and S A4 222 - 4 ) of the full-bridge converter 214 ( FIG. 2 ).
- a reference waveform e.g., a triangular waveform
- control system 800 includes a detection circuit configured to detect when the input power source has a missing phase or is running under a single-phase condition and to generate control signals to be used by the command interface 812 to shut off the switches in one or more phase-legs of the universal auto-transformer.
- the universal auto- transformer may be dynamically configured.
- FIG. 9 is a flow diagram of an embodiment of a process of operation 900 of a universal transformer.
- a first switched converter circuit is configured for step-up or step-down conversion including a first number of conversion levels 910 .
- a second switched converter circuit is configured for step-up or step-down conversion including a second number of conversion levels 912 .
- a direction of power flow is optionally configured 914 .
- Frequencies of input and/or output signals are optionally configured 916 .
- a number of phases of the input and/or output signals is optionally configured 918 .
- the process of operation 900 may include fewer operations or additional operations. An order or position of two or more operations may be changed. Two or more operations may be combined into a single operation.
- Devices and circuits described herein can be implemented using computer aided design tools available in the art, and embodied by computer readable files containing software descriptions of such circuits, at behavioral, register transfer, logic component, transistor, and layout geometry level descriptions stored on storage media or communicated by carrier waves.
- Data formats in which such descriptions can be implemented include, but are not limited to, formats supporting behavioral languages like C; formats supporting register transfer level RTL languages like Verilog and VHDL; and formats supporting geometry description languages like GDSII, GDSIII, GDSIV, CIF, MEBES, and other suitable formats and languages.
- Data transfers of such files on machine readable media including carrier waves can be done electronically over the diverse media on the Internet or through email, for example.
- Physical files can be implemented on machine readable media such as 4 mm magnetic tape, 8 mm magnetic tape, 31 ⁇ 2 inch floppy media, CDs, DVDs, and so on.
- FIG. 10 is a block diagram an embodiment of a system 1000 for storing computer readable files containing software descriptions of the circuits.
- the system 1000 may include at least one data processor or central processing unit (CPU) 1010 , a memory 1014 , and one or more signal lines 1012 for coupling these components to one another.
- the one or more signal lines 1012 may constitute one or more communications busses.
- the memory 1014 may include high-speed random access memory and/or non-volatile memory, such as one or more magnetic disk storage devices.
- the memory 1014 may store a circuit compiler 1016 and circuit descriptions 1018 .
- the circuit descriptions 1018 may include circuit descriptions for one or more converter circuits 1020 , one or more energy storage devices 1022 , one or more duty-cycle modulation circuits 1024 , one or more filter circuits 1026 , and semiconductor switches 1028 .
Abstract
A power conversion device includes a first switched converter circuit coupled to a device input and a second switched converter circuit coupled to the first switched converter circuit and a device output. The first switched converter circuit and the second switched converter circuit may be configurable for multi-level step-up and/or step-down conversion.
Description
- This application is a continuation-in-part of pending U.S. patent application Ser. No. 11/438,785, filed May 22, 2006; which is a continuation of U.S. patent application Ser. No. 10/723,621, filed Nov. 25, 2003, now U.S. Pat. No. 7,050,311; and is a continuation-in-part of pending U.S. patent application Ser. No. 11/246,800, filed Oct. 7, 2005; which is a divisional of U.S. patent application Ser. No. 10/723,620, filed Nov. 25, 2003, now U.S. Pat. No. 6,954,366. Each of the foregoing applications and patents are incorporated by reference herein in their entireties.
- The present invention relates generally to power conversion technology and in particular to a universal autotransformer for enhancing the functionality of power conversion.
- Transformers have numerous applications including voltage or current conversion, impedance matching and electrical isolation. As a consequence, transformers are widely used throughout the world, forming the backbone of electric power conversion systems, and make up a large portion of power delivery systems. The positive attributes of conventional transformers have been well documented for years and include low cost, high reliability, and high efficiency. Were it not for these highly reliable devices, activities such as recharging batteries in a portable device or consumers receiving power from a distant electric generator would be prohibitively expensive, resulting in electricity being a much less practical form of energy.
- Autotransformers are a subset of transformers in which primary and secondary coils have some or all of their windings in common.
FIG. 1 illustrates aconventional autotransformer 100 that may be used to convert aninput V 1 110, having a first ac voltage and current level and a first frequency, to anoutput V 2 112, having a second ac voltage and current level and a second frequency equal to the first frequency. Conventional autotransformers, such as theconventional autotransformer 100, typically utilize a copper and iron-based core to perform such a power transformation. In the conventional auto-transformer 100, the second ac voltage and current level may be adjusted by selecting a number of windings or taps in the core that are coupled to theoutput V 2 112. - Conventional auto-transformers, however, have some drawbacks. The first voltage of the
input V 1 110 is typically higher than the second voltage of theoutput V 2 112. Power typically flows only from the primary side to the secondary side. In addition, the voltage of theoutput V 2 112 drops under load; there is a sensitivity to harmonics generated in a load; environmental impacts occur if mineral oil in the core leaks; there is little or no flexibility in adjusting the power conversion (including voltages/currents, and/or the first or second frequencies); and there is no energy-storage capacity. One consequence of not having energy storage capacity is that theoutput V 2 112 can be easily interrupted because of a disturbance at theinput V 1 110. - There is a need, therefore, for improved auto-transformers.
- A multilevel intelligent universal transformer includes power electronics on a primary side and on a secondary side to enhance the functionality of power conversion. The multilevel intelligent universal transformer may be an auto-transformer.
- In some embodiments, a power conversion device includes a first switched converter circuit coupled to a device input and a second switched converter circuit coupled to the first switched converter circuit and a device output. The first switched converter circuit and the second switched converter circuit may be configurable for multi-level step-up and/or step-down conversion.
- The first switched converter circuit and the second switched converter circuit may be configured to utilize duty-cycle modulation to implement the multi-level step-up and/or step-down conversion.
- An energy storage device (e.g., ultra-capacitor) may be coupled between the first switched converter circuit and the second switched converter circuit to mitigate voltage disturbances.
- A first filter may be coupled to an input of the first switched converter circuit and/or a second filter may be coupled to an output of the second switched converter circuit. The first filter and the second filter may be configured to provide substantially sinusoidal signals.
- The first switched converter circuit may include a first plurality of configurable semiconductor switches and second switched converter circuit may include a second plurality of configurable semiconductor switches.
- In some embodiments, the first switched converter circuit is configured to adjust a first number of conversion levels of signals at the device input, and/or the second switched converter circuit is configured to adjust a second number of conversion levels of signals at the device output.
- In some embodiments, the first switched converter circuit is a half-bridge or a full-bridge converter. In some embodiments, the second switched converter circuit is a half-bridge or a full-bridge converter.
- In some embodiments, the device is configurable for bidirectional power flow. In some embodiments, a frequency of signals at the device output is configurable.
- In some embodiments, the first switched converter circuit is configured to receive signals at the device input having 3-phases separated by approximately 120°. In some embodiments, the second switched converter circuit is configured to output signals at the device output having 3-phases separated by approximately 120°.
- A significant advantage of the present invention is the combining of the functionalities of one or more custom power devices into a single, tightly integrated, electrical device, rather than the costly conventional solution of utilizing separate custom power devices.
-
FIG. 1 is a circuit diagram illustrating a conventional auto-transformer; -
FIG. 2 is a circuit diagram illustrating an embodiment of a universal transformer; -
FIG. 3 is a circuit diagram illustrating an embodiment of a universal transformer; -
FIG. 4 is a circuit diagram illustrating an embodiment of a universal transformer; -
FIG. 5 is a circuit diagram illustrating an embodiment of a universal transformer; -
FIG. 6 is a circuit diagram illustrating an embodiment of a universal transformer; -
FIG. 7 is a circuit diagram illustrating an embodiment of a universal transformer; -
FIG. 8 is a circuit diagram illustrating an embodiment of a control system; -
FIG. 9 is a flow diagram illustrating an embodiment of a process of operation of a universal transformer; and -
FIG. 10 is a block diagram illustrating an embodiment of a system. - Like reference numerals refer to corresponding parts throughout the drawings.
- Reference will now be made in detail to embodiments of a multilevel intelligent universal auto-transformer (henceforth referred to as a universal auto-transformer), examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components and circuits have not been described in detail so as not to unnecessarily obscure aspects of the embodiments.
- The universal auto-transformer utilizes modern power electronics to replace the core in a conventional auto-transformer and thereby enhances the power conversion functionality. In some embodiments, the universal auto-transformer includes a plurality of power semiconductor switches in at least first and second switched converter circuits corresponding to the primary side and the secondary side, respectively, of a conventional auto-transformer.
- The universal auto-transformer may include an energy storage device, such as one or more capacitors, between the first and the second switched converter circuits. The energy storage device may serve as the energy buffer in between the source and load to avoid direct impact from either the load to the source or the source to the load. The energy storage device may allow the universal auto-transformer to at least partially compensate for outages, where input signals to the universal auto-transformer are temporarily reduced (such as voltage sag) or disrupted.
- The power electronic switches in the first and the second switched converter circuits may allow the universal auto-transformer to be configured in a variety of ways. The universal auto-transformer may be configured for one of a range of step-up or step-down voltage and/or current conversions. A voltage and/or current of the output signals may be regulated. Harmonics generated by nonlinearities in a load, as seen from the input, may be reduced or eliminated. A frequency of the output signals may be adjusted and/or selected (e.g., DC, 50 Hz, 60 Hz, 400 Hz, etc.). The input and/or the output signals may be approximately uni-phase or poly-phase, such as tri-phase signals where signals are separated by approximately 120°. In addition, the universal auto-transformer may be configured for bidirectional power flow. For example, power may flow from the primary side to the secondary side or from the secondary side to the primary side.
- These features allow the universal auto-transformer to integrate the functionalities of one or more custom power devices. Such a “hybrid” universal auto-transformer thereby overcomes at least some of the deficiencies of existing auto-transformers, such as the conventional auto-
transformer 100, in a cost effective manner. -
FIG. 2 is a circuit diagram illustrating an embodiment of auniversal transformer 200. Theuniversal transformer 200 illustrates a multilevel converter single-phase to single-phase step-down auto-transformer. Theuniversal transformer 200 includes a 3-level full-bridge converter 214, a 3-level half-bridge converter 216, and anenergy storage device 218. Theuniversal transformer 200 has a supply voltage Vd, a common voltage VCd, and a ground GND. The 3-level full-bridge converter 214 on the primary side includes two groups of four switches SA 222 and SB 224, as well as anti-parallel diode protection. The 3-level half-bridge converter 216 on the secondary side includes four switches SC 226 and anti-parallel diode protection. - The
energy storage device 218 includes a plurality of capacitors, connected in series, that are in parallel with an output from the 3-level full-bridge converter 214 and an input to the 3-level half-bridge converter 216. In some embodiments, theenergy storage device 218 may include a battery. Theenergy storage device 218 may be any DC voltage source capable of maintaining voltage for a sufficient period of time to compensate for a disturbance or interruption, such as an outage, and may include capacitor banks, ultra-capacitors, flywheels, batteries, or any other suitable storage media (or any combination thereof). If theuniversal transformer 200 is used in an application or system that requires outage compensation or short-term interruption protection, theenergy storage device 218 may allow theuniversal transformer 200 to ride-through these disturbances. When a voltage of aninput V 1 210 drops for a short period of time, theenergy storage device 218 may compensate for the deficit and maintain constant voltage amplitude for anoutput V 2 212. The total period of compensation as a function of the amount of energy storage may be adapted as desired. In some embodiments, an additional device, such as a battery, in theenergy storage device 218 may be switched into theuniversal transformer 200 upon detection of a voltage sag and/or to provide outage compensation. - The
universal transformer 200 converts theinput V 1 210 to theoutput V 2 212. Duty cycle modulation of signals (for example, using pulse width modulation) controlling the switches SA 222, SB 224, and/or SC 226 allows the step-down voltage (between theinput V 1 210 and the output V2 212) to be adjusted and/or configured. In an exemplary embodiment, a common duty cycle is used for control signals to the switches SA 222, SB 224, and SC 226, and a voltage amplitude of theinput V 1 210 is approximately twice the voltage amplitude of theoutput V 2 212. In this example, power is flowing from the primary side to the secondary or load side. The 3-level full-bridge converter 214 functions as a converter, and the 3-level half-bridge converter 216 functions as an inverter. In other embodiments, power may flow from the secondary side to the primary side. In this case, the 3-level full-bridge converter 214 functions as a inverter, and the 3-level half-bridge converter 216 functions as a converter - The
inductors L 1 220 andL 2 228 in conjunction with an input and an output capacitance, respectively, form low-pass filters to provide filtering of high frequencies signals and/or smoothing of noise. In this way, theinput V 1 210 is approximately sinusoidal having the first frequency and/or theoutput V 2 212 is approximately sinusoidal having the second frequency. An approximately sinusoidal signal has substantially reduced ripple. In some embodiments, the first frequency may be different that the second frequency (e.g., DC, 50 Hz, 60 Hz, or 400 Hz) depending on the duty cycle modulation of the switches SA 222, SB 224, and/or SC 226. Note that other combinations of passive and/or active devices can be coupled to the primary side and/or the secondary side of theuniversal transformer 200 to provide filtering using well-known filter design techniques. - The switches SA 222, SB 224, and/or SC 226 may be semiconductor switches that may be rapidly switched (approximately at 30,000 to 40,000 Hz). The switches SA 222, SB 224, and/or SC 226 may include Gate-Turn-Off (GTO) Thyristors, Integrated Gate Bipolar Transistors (IGBTs), MOS Turn-off Thyristors (MTOs), Integrated-Gate Commutated Thyristors (IGCTs), Silicon Controlled Rectifiers (SCRs), or any other semiconductor devices that have a turn-off capability.
- In addition to performing power conversion and/or adjustment or selection of the second frequency, the
universal transformer 200 will also isolate the voltage of theinput V 1 210 and the current from theoutput V 2 212. Thus, transients, such as those generated by a power factor correction capacitor switching event, will not propagate to the secondary or load side of theuniversal transformer 200. In addition, harmonics, such as those generated in a non-linear load or by reactive power in the load, will not propagate to the primary side. This may be accomplished by actively switching the switches SA 222 and SB 224 in the full-bridge converter 214 such that an input current becomes sinusoidal and in phase with the voltage of theinput V 1 210. - In some embodiments, the
universal transformer 200 may include fewer components or additional components. For example, a number of switches and/or their switching frequency may be different from that illustrated in theuniversal transformer 200. Functions of two or more components may be combined. An order or relative position of two or more components may be interchanged. -
FIG. 3 is a circuit diagram illustrating an embodiment of auniversal transformer 300. Theuniversal transformer 300 converts theinput V 1 310 to theoutput V 2 312 using a 5-level full-bridge converter 314, a 5-level half-bridge converter 316, and anenergy storage device 318. Theuniversal transformer 300 has a supply voltage Vd, a common voltage VCd, and a ground GND. The 5-level full-bridge converter 314 on the primary side includes two groups of eight switches SA 322 and SB 324, as well as anti-parallel diode protection. The 5-level half-bridge converter 316 on the secondary side includes eight switches SC 328 and anti-parallel diode protection. Theenergy storage device 318 includes a plurality of capacitors 326, connected in series, that are in parallel with an output from the 5-level full-bridge converter 314 and an input to the 5-level half-bridge converter 316. In some embodiments, theenergy storage device 318 may include an additional device, such as a battery, as described above for the universal auto-transformer 200 (FIG. 2 ). The universal auto-transformer 300 may also includeinductors L 1 320 andL 2 330 or other active or passive components to provide filtering of high frequencies signals and/or smoothing of noise. - While the function of the switches SA 322, SB 324, and SC 328 and the universal auto-transformer 300 (and the switches in the embodiments described below) as a whole is similar to that of the switches SA 222, SB 224, and SC 226 (
FIG. 2 ) and the universal auto-transformer 200 (FIG. 2 ), increasing the number of levels (and switches) has advantages for higher voltage applications. Each of the switches SA 322, SB 324, and SC 328 only needs to block a quarter of the DC bus voltage. As a consequence, theuniversal transformer 300 may be used with higher high-voltages for theinput V 1 310 and/or theoutput V 2 312 without using higher voltage devices for the switches SA 322, SB 324, and/or SC 328. - In some embodiments, the
universal transformer 300 may include fewer components or additional components. For example, a number of switches and/or their switching frequency may be different from that illustrated in theuniversal transformer 300. Functions of two or more components may be combined. An order or relative position of two or more components may be interchanged. - For higher voltages, the number of converter levels and switches may be further increased, as illustrated in
FIG. 4 , which shows is a circuit diagram of an embodiment of auniversal transformer 400. Theuniversal transformer 400 converts theinput V 1 410 to theoutput V 2 412 using an 11-level full-bridge converter 414, an 11-level half-bridge converter 416, and anenergy storage device 418. Theuniversal transformer 400 has a supply voltage Vd, a common voltage VCd, and a ground GND. The 11-level full-bridge converter 414 on the primary side includes two groups of 20 switches SA and SB, as well as anti-parallel diode protection. The 11-level half-bridge converter 416 on the secondary side includes 20 switches SC and anti-parallel diode protection. Theenergy storage device 418 includes a plurality of capacitors C, connected in series, that are in parallel with an output from the 11-level full-bridge converter 414 and an input to the 11-level half-bridge converter 416. In some embodiments, theenergy storage device 418 may include an additional device, such as a battery, as described above for the universal auto-transformer 200 (FIG. 2 ). The universal auto-transformer 400 may also includeinductors L 1 420 andL 2 422 or other active or passive components to provide filtering of high frequencies signals and/or smoothing of noise. In an exemplary embodiment, theinput V 1 410 is 345 kV and theoutput V 2 412 is 220 kV. - In some embodiments, the
universal transformer 400 may include fewer components or additional components. For example, a number of switches and/or their switching frequency may be different from that illustrated in theuniversal transformer 400. Functions of two or more components may be combined. An order or relative position of two or more components may be interchanged. - If the primary and the secondary sides of a universal auto-transformer have the same or similar voltages levels, the device can be simplified, for example, by using half-bridge converters on both sides of the universal auto-transformer. This is illustrated in FIG. 5, which shows an embodiment of a
universal transformer 500. Theuniversal transformer 500 converts theinput V 1 510 to theoutput V 2 512 using a 3-level half-bridge converter 514, a 3-level half-bridge converter 516, and anenergy storage device 518. Theuniversal transformer 500 has a supply voltage Vd, a common voltage VCd, and a ground GND. The 3-level half-bridge converter 514 on the primary side includes four switches SA 522 and anti-parallel diode protection. The reduced number of switches in thisembodiment 500 reduces the overall cost. The 3-level half-bridge converter 516 on the secondary side includes four switches SB 524 and anti-parallel diode protection. Theenergy storage device 518 includes a plurality of capacitors, connected in series, that are in parallel with an output from the 3-level half-bridge converter 514 and an input to the 3-level half-bridge converter 516. In some embodiments, theenergy storage device 518 may include an additional device, such as a battery, as described above for the universal auto-transformer 200 (FIG. 2 ). The universal auto-transformer 500 may also includeinductors L 1 520 andL 2 526 or other active or passive components to provide filtering of high frequencies signals and/or smoothing of noise. - In some embodiments, the
universal transformer 500 may include fewer components or additional components. For example, a number of switches and/or their switching frequency may be different from that illustrated in theuniversal transformer 500. Functions of two or more components may be combined. An order or relative position of two or more components may be interchanged. - As illustrated in the preceding discussion, the number of configurable switches on the primary and/or the secondary side of the universal auto-transformer may be selected and/or configured. In some embodiments, a first number of switches in the converter circuit on the primary side is based on a voltage of signals at the device input and a voltage limit of the switches in the converter circuit on the primary side. In some embodiments, a second number of switches in the converter circuit on the secondary side is based on a voltage of signals at the device output and a voltage limit of the switches in the converter circuit on the secondary side. For example, the first number of switches may be increased if the voltage of signals at the device input is increased and/or the voltage limit of the switches in the converter circuit on the primary side is decreased.
- As illustrated in embodiments 200 (
FIG. 2 ), 300 (FIG. 3 ), 400 (FIG. 4 ), and 500, the first number of switches in the converter on the primary side and/or the second number of switches in the converter on the secondary side may vary based on the design and/or application considerations. In some embodiments, the first number of switches equals 2(N1−1), 3(N1−1), 4(N1−1), or 6(N1−1), where N1 is a number of conversion levels of the signals at the device input. In some embodiments, the second number of switches equals 2(NO−1), 3(NO−1), 4(NO−1), and 6(NO−1), where NO is a number of conversion levels of the signals at the device output. For example, for 3 conversion levels, the number of switches in a half-bridge converter circuit may be 4, and the number of switches in a full-bridge converter circuit may be 8. - In some embodiments, full-bridge converters may be used on both the primary and the secondary side of the universal auto-transformer. While the second number of switches is doubled relative to embodiments such as the universal auto-transformer 200 (
FIG. 2 ), the maximum voltage of the output is also doubled. This is illustrated inFIG. 6 , which shows an embodiment of auniversal transformer 600. Theuniversal transformer 600 converts theinput V 1 610 to theoutput V 2 612 using a 3-level full-bridge converter 614, a 3-level full-bridge converter 616, and anenergy storage device 618. Theuniversal transformer 600 has a supply voltage Vd, a common voltage VCd, and a ground GND. The 3-level full-bridge converter 614 on the primary side includes two groups of four switches SA 622 and SB 624, as well as anti-parallel diode protection. The 3-level full-bridge converter 616 on the secondary side includes two groups of four switches SC 628 and SD 630, as well as anti-parallel diode protection. Theenergy storage device 618 includes a plurality of capacitors C 626, connected in series, that are in parallel with an output from the 3-level full-bridge converter 614 and an input to the 3-level full-bridge converter 616. In some embodiments, theenergy storage device 618 may include an additional device, such as a battery, as described above for the universal auto-transformer 200 (FIG. 2 ). The universal auto-transformer 600 may also includeinductors L 1 620 andL 2 632 or other active or passive components to provide filtering of high frequencies signals and/or smoothing of noise. - In some embodiments, the
universal transformer 600 may include fewer components or additional components. For example, a number of switches and/or their switching frequency may be different from that illustrated in theuniversal transformer 600. Functions of two or more components may be combined. An order or relative position of two or more components may be interchanged. - The universal auto-transformer may also be configured and/or used to convert single-phase input signals into poly-phased output signals. This is illustrated in
FIG. 7 , which shows a circuit diagram illustrating an embodiment of auniversal transformer 700. Theuniversal transformer 700 converts theinput V 1 710 to a three-phase the output V2 712 (having approximately 120° between the signals) using a 3-level half-bridge converter 714, a 3-level half-bridge converter 716, and anenergy storage device 718. Theuniversal transformer 700 has a supply voltage Vd, a common voltage VCd, and a ground GND. The 3-level half-bridge converter 714 on the primary side includes four switches SA 722 and anti-parallel diode protection. The 3-level half-bridge converter 716 on the secondary side includes three groups of four switches SB 724, SC 726, and SD 728, as well as anti-parallel diode protection. Theenergy storage device 718 includes a plurality of capacitors, connected in series, that are in parallel with an output from the 3-level half-bridge converter 714 and an input to the 3-level half-bridge converter 716. In some embodiments, theenergy storage device 718 may include an additional device, such as a battery, as described above for the universal auto-transformer 200 (FIG. 2 ). The universal auto-transformer 700 may also includeinductors L 1 720 andL 2 730 or other active or passive components to provide filtering of high frequencies signals and/or smoothing of noise. - In some embodiments, the
universal transformer 700 may include fewer components or additional components. For example, a number of switches and/or their switching frequency may be different from that illustrated in theuniversal transformer 700, such as would be needed if one or more full-bridge converters are used instead of half-bridge converters. Alternatively, poly-phase input signals may be converted into single-phase output signals. Functions of two or more components may be combined. An order or relative position of two or more components may be interchanged. - Referring to
FIG. 2 , the universal auto-transformer 200 is used as an illustrative example of the operation of other embodiments of the universal auto-transformer. The basic operation is to switch first pair of switches SA1 222-1 and SA2 222-2 and second pair of switches SB3 224-3 and SB4 224-4, and to switch third pair of switches SA3 222-3 and SA4 222-4 and fourth pair of switches SB1 224-1 and SB2 224-2, in an alternating fashion such that an output of the 3-level half-bridge converter 216 is an alternating chopped DC voltage. The switches SC 226 are similarly paired and switched. The filter associated withL 2 228 smoothes the resulting chopped DC voltage into a clean, sinusoidal waveform. - The switches SA 222, SB 224, and/or SC 226 may be controlled by an external control means using either analog or digital control signals in a manner commonly known to one of ordinary skill in the art. For example, the states of switches SA 222, SB 224, and/or SC 226 may be controlled using pulse-width modulation (PWM) techniques. In PWM, the width of pulses in a pulse train are modified in direct proportion to a small control voltage. By using a sinusoid of a desired frequency as the control voltage, it is possible to produce a waveform whose average voltage varies sinusoidally in a manner suitable for driving the switches SA 222, SB 224, and/or SC 226.
- Signals used for driving the switches SA 222, SB 224, and/or SC 226 may be provided by a control system. This is illustrated in
FIG. 8 , which is a circuit diagram showing an embodiment of afeedback control system 800. Thefeedback control system 800 includes a processor 806 (e.g., microcomputer, digital signal processor), ascaling factor circuit 808, a set ofgate drivers 810, and acommand interface 812. The processor further includes apulse width modulator 814, acontroller 816, and memory 818 (e.g., DRAM, CD-ROM). Thescaling factor circuit 808 and thegate drivers 810 isolate control signals from the power. - In operation, the
processor 806 compares a command voltage, Vref, and a scaled feedback output signal, Vsense, to determine an error signal, Verror. The feedback signal, Vsense, is taken from the output of theconverter 802. The error signal, Verror, is received by thecontroller 816, which generally applies a proportional (P), proportional-integral (PI), or proportional-integral-differentiator (PID) gain to the error signal. The output of the controller is a smooth duty cycle signal, d(t). Note that in a typical application either a load (e.g., adjustable speed drive) or anotherconverter 804 is coupled to the output of theconverter 802. - The duty cycle of each switch in the
converter 802 is computed by theprocessor 806 based on one or more computer programs or gate pattern logic stored in thememory 818. The resulting duty cycle signal, d(t), is then sent to the pulse width modulator 814 (PWM), which generally includes a set of voltage comparators. In some embodiments, one comparator is used for each pair of switches. For example, the switch pair SA1 222-1 and SA2 222-2 (FIG. 2 ) in the actively switched full-bridge converter 214 (FIG. 2 ) may be controlled by a first comparator, and the switch pair SA3 222-3 and SA4 222-4 (FIG. 2 ) may be controlled by a second comparator. The PWM signals are then fed into thegate drivers 810 to turn the switches in theconverter 802 on or off. The number of switches in theconverter 802 depends on how many voltage levels and phases are to be controlled. - The control voltages d(t) (and therefore the output pulse width) can be varied to achieve different frequencies and voltage levels in any desired manner. For example, the
processor 806 can implement various acceleration and deceleration ramps, current limits, and voltage-versus-frequency curves by changing variables (e.g., via the command interface 812) in control programs or gate pattern logic inprocessor 806. - If the duty cycle d(t) is greater than the voltage level of a reference waveform (e.g., a triangular waveform) at any given time t, then the
PWM circuit 814 will turn on the upper switches (e.g., switches SA1 222-1 and SA2 222-2) of the full-bridge converter 214 (FIG. 2 ) and turn off the lower switches (e.g., switches SA3 222-3 and SA4 222-4) of the full-bridge converter 214 (FIG. 2 ). For a three-phase PWM inverter embodiment (e.g., theembodiment 700 shown inFIG. 7 ), three single-phase control circuits may be used with control voltages comprising sinusoidal waveforms shifted by approximately 120° between phases using techniques well-known in the art. - In some embodiments, the
control system 800 includes a detection circuit configured to detect when the input power source has a missing phase or is running under a single-phase condition and to generate control signals to be used by thecommand interface 812 to shut off the switches in one or more phase-legs of the universal auto-transformer. - As noted in the previous discussion, in some embodiments the universal auto- transformer may be dynamically configured. This is illustrated in
FIG. 9 , which is a flow diagram of an embodiment of a process ofoperation 900 of a universal transformer. A first switched converter circuit is configured for step-up or step-down conversion including a first number of conversion levels 910. A second switched converter circuit is configured for step-up or step-down conversion including a second number of conversion levels 912. A direction of power flow is optionally configured 914. Frequencies of input and/or output signals are optionally configured 916. A number of phases of the input and/or output signals is optionally configured 918. The process ofoperation 900 may include fewer operations or additional operations. An order or position of two or more operations may be changed. Two or more operations may be combined into a single operation. - Devices and circuits described herein can be implemented using computer aided design tools available in the art, and embodied by computer readable files containing software descriptions of such circuits, at behavioral, register transfer, logic component, transistor, and layout geometry level descriptions stored on storage media or communicated by carrier waves. Data formats in which such descriptions can be implemented include, but are not limited to, formats supporting behavioral languages like C; formats supporting register transfer level RTL languages like Verilog and VHDL; and formats supporting geometry description languages like GDSII, GDSIII, GDSIV, CIF, MEBES, and other suitable formats and languages. Data transfers of such files on machine readable media including carrier waves can be done electronically over the diverse media on the Internet or through email, for example. Physical files can be implemented on machine readable media such as 4 mm magnetic tape, 8 mm magnetic tape, 3½ inch floppy media, CDs, DVDs, and so on.
-
FIG. 10 is a block diagram an embodiment of asystem 1000 for storing computer readable files containing software descriptions of the circuits. Thesystem 1000 may include at least one data processor or central processing unit (CPU) 1010, amemory 1014, and one ormore signal lines 1012 for coupling these components to one another. The one ormore signal lines 1012 may constitute one or more communications busses. - The
memory 1014 may include high-speed random access memory and/or non-volatile memory, such as one or more magnetic disk storage devices. Thememory 1014 may store acircuit compiler 1016 andcircuit descriptions 1018. Thecircuit descriptions 1018 may include circuit descriptions for one ormore converter circuits 1020, one or moreenergy storage devices 1022, one or more duty-cycle modulation circuits 1024, one ormore filter circuits 1026, and semiconductor switches 1028. - The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.
Claims (20)
1. A power conversion device, comprising:
a first switched converter circuit coupled to a device input; and
a second switched converter circuit coupled to the first switched converter circuit and a device output,
wherein the first switched converter circuit and the second switched converter circuit are configurable for multi-level step-up or step-down conversion.
2. The device of claim 1 , wherein the first switched converter circuit is a full-bridge converter.
3. The device of claim 1 , wherein the first switched converter circuit is a half-bridge converter.
4. The device of claim 1 , wherein the second switched converter circuit is a full-bridge converter.
5. The device of claim 1 , wherein the second switched converter circuit is a half-bridge converter.
6. The device of claim 1 , wherein the first switched converter circuit and the second switched converter circuit comprise a symmetric half-bridge converter pair.
7. The device of claim 1 , wherein the first switched converter circuit and the second switched converter circuit comprise a symmetric full-bridge converter pair.
8. The device of claim 1 , wherein the first switched converter circuit and the second switched converter circuit are configured to utilize duty-cycle modulation to implement the multi-level step-up or step-down conversion.
9. The device of claim 1 , further comprising an energy storage device coupled between the first switched converter circuit and the second switched converter circuit to mitigate voltage disturbances.
10. The device of claim 1 , further comprising:
a first filter coupled to an input of the first switched converter circuit; and
a second filter coupled to an output of the second switched converter circuit,
wherein the first filter and the second filter are configured to provide substantially sinusoidal signals.
11. The device of claim 1 , wherein the first switched converter circuit implements 3-level conversion and the second switched converter circuit implements 3-level conversion.
12. The device of claim 1 , wherein the first switched converter circuit implements 5-level conversion and the second switched converter circuit implements 5-level conversion.
13. The device of claim 1 , wherein the first switched converter circuit may be configured to adjust a first number of conversion levels of signals at the device input and the second switched converter circuit may be configured to adjust a second number of conversion levels of signals at the device output.
14. The device of claim 1 , wherein the first switched converter circuit includes a first plurality of configurable semiconductor switches and second switched converter circuit includes a second plurality of configurable semiconductor switches.
15. The device of claim 14 , wherein a first number of configurable semiconductor switches in the first plurality of configurable semiconductor switches is selected based on a voltage level of signals at the device input and a voltage limit of the first plurality configurable semiconductor switches, and a second number of configurable semiconductor switches in the second plurality of configurable semiconductor switches is selected based on a voltage level of signals at the device output and a voltage limit of the second plurality configurable semiconductor switches.
16. The device of claim 15 , wherein a first number of configurable semiconductor switches in the first plurality of configurable semiconductor switches is selected from a group consisting of 2(N1−1), 3(N1−1), 4(N1−1), and 6(N1−1), where N1 is a number of conversion levels of the signals at the device input, and wherein a second number of configurable semiconductor switches in the second plurality of configurable semiconductor switches is selected from a group consisting of 2(NO−1), 3(NO−1), 4(NO−1), and 6(NO−1), where NO is a number of conversion levels of the signals at the device output.
17. The device of claim 1 , wherein the device is configurable for bidirectional power flow.
18. The device of claim 1 , wherein a frequency of signals at the device output is configurable.
19. The device of claim 1 , wherein the first switched converter circuit is configured to receive signals at the device input having 3-phases separated by substantially 120°.
20. The device of claim 1 , wherein the second switched converter circuit is configured to output signals at the device output having 3-phases separated by substantially 120°.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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US11/705,077 US20070230226A1 (en) | 2003-11-25 | 2007-02-08 | Multilevel intelligent universal auto-transformer |
Applications Claiming Priority (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/723,621 US7050311B2 (en) | 2003-11-25 | 2003-11-25 | Multilevel converter based intelligent universal transformer |
US10/723,620 US6954366B2 (en) | 2003-11-25 | 2003-11-25 | Multifunction hybrid intelligent universal transformer |
US11/246,800 US20060028848A1 (en) | 2003-11-25 | 2005-10-07 | Multifunction hybrid intelligent universal transformer |
US11/438,785 US20060221653A1 (en) | 2003-11-25 | 2006-05-22 | Multilevel converter based intelligent universal transformer |
US11/705,077 US20070230226A1 (en) | 2003-11-25 | 2007-02-08 | Multilevel intelligent universal auto-transformer |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US11/438,785 Continuation-In-Part US20060221653A1 (en) | 2003-11-25 | 2006-05-22 | Multilevel converter based intelligent universal transformer |
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US20070230226A1 true US20070230226A1 (en) | 2007-10-04 |
Family
ID=38533191
Family Applications (1)
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US11/705,077 Abandoned US20070230226A1 (en) | 2003-11-25 | 2007-02-08 | Multilevel intelligent universal auto-transformer |
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